In recent years, jet-propulsion personal watercrafts (PWC) have been widely used in leisure, sport, rescue activities, and the like. The watercraft is typically equipped with an engine in an inner space defined by a hull and a deck forming a body. The engine drives a water jet pump, which pressurizes and accelerates the water that is sucked from a water intake, which is generally provided on a hull bottom surface and ejects it rearward from an outlet port. As the resulting reaction, the watercraft is propelled forward.
In such jet-propulsion personal watercrafts, when a driver operates a throttle lever to close a throttle valve for deceleration of the watercraft, and thereby turns the engine to an idling state while the watercraft is driving on the water surface, a propulsion force for steering the body becomes small. So, when making the watercraft approach a position parallel to a shoreline, the driver must steer a steering handle while manipulating the throttle lever.
A conventional jet-propulsion personal watercraft is equipped with an actuator to restrict a closed position of a throttle valve, which is subjected to a force applied from a return spring in a direction to close the throttle valve. In this watercraft, even when the throttle lever is operated by the driver to close the throttle valve while driving, the actuator restricts a closing operation of the throttle valve immediately before an engine speed reaches an idling engine speed, so that the engine speed is maintained slightly higher than the idling engine speed for a certain time period. This makes it possible to retard time when the engine speed reaches the idling engine speed so that a suitable propulsion force is maintained without a need for the driver to manipulate the throttle lever carefully. Thus, the watercraft can be steered effectively for a longer time period.
However, if the time when the engine speed reaches the idling engine speed is retarded in a case where the watercraft is driving only straight ahead in a deceleration state, the propulsion force is maintained, increasing a distance over which the watercraft is moved until it is stopped. Therefore, in the case where the watercraft is driving only straight ahead in the deceleration state, it is necessary to quickly reduce the engine speed so that the distance over which the watercraft is moved until it is stopped does not become long.